Applicants, national Offices, receiving Offices, International Searching and Preliminary Examining Authorities, and the International Bureau, shall, for the purposes of the Treaty and the Regulations, express any date in terms of the Christian era and the Gregorian calendar, or, if they use other eras and calendars, they shall also express any date in terms of the Christian era and the Gregorian calendar.
Source: http://www.wipo.int/pct/en/texts/articles/r79.htm
Date retrieved: 17 May 2021